After an invasive surgical operation on a joint (e.g. total knee replacement, total hip replacement, anterior cruciate ligament reconstruction), the joint and surrounding bodily parts are often left in a weakened state, requiring immediate rehabilitation. For patients recovering from extensive joint surgery, any attempt at joint motion causes extreme pain. Consequently, patients tend to avoid substantial movement of the limb. This “immobilization” allows the tissue around the joint to become stiff and for scar tissue to form. These undesirable effects lead to limited range of motion in the joint and prolong physical therapy before the joint and limb regain substantial range of motion, neurological function and muscle function. If full range of motion of the joint and limb is not achieved in the immediate or early postoperative period, then the full range of motion may never be recovered.
Another complication that occurs during the postoperative period following surgery on a patient's joint is deep vein thrombosis (DVT). DVT is the formation of blood clots in a deep vein of the patient's limb, which can block blood flow and cause swelling and pain. DVT becomes most serious when a portion of the clot dislodges, travels through the bloodstream to the lungs or brain, and blocks blood flow therein. Several methods of preventing or limiting the chances of developing DVT include the application of pressure to the limb or periodic movement of the limb to promote increased blood flow in the veins. With greater blood flow circulation, clots are less likely to occur.
Continuous passive motion (CPM) devices are often used during early phases of postoperative rehabilitation to provide passive motion to the treated joint and limb, to control postoperative pain, and reduce inflammation. Typical CPM devices continuously move a patient's limb and joint through a predetermined range of motion without exertion by the patient. The passive motion acts to pump blood and edema fluid away from the joint and surrounding tissue. As a result, CPM devices reduce joint stiffness and improve venous blood flow. Despite their therapeutic benefits, these devices fail to produce a complete range of motion in the patient's limb because the muscles therein may not fully extend and contract. Further, CPM devices have shown only limited effectiveness on DVT prevention. In order to overcome these shortcomings and provide a more comprehensive therapeutic treatment, other modalities or forms of stimulation are incorporated with the CPM devices. For instance, to increase a patient's chances of regaining full range of motion, neuromuscular stimulation (NMS) (e.g. functional electrical stimulation) can be combined with the CPM device. This electrophysical modality transmits electrical impulses to the muscles to effect total joint extension and contraction. Alternatively, a CPM device can be combined with a prophylactic therapy to hinder DVT development. Therefore, CPM devices that simultaneously provide passive motion and other stimulating modalities improve the patient's likelihood of regaining full range of motion in the joint and limb without postoperative complications and excessive pain.
Some CPM devices have incorporated an NMS modality to promote range of motion in the limb. For example, U.S. Pat. No. 4,520,827 to Wright et al. discloses a rehab apparatus comprising a CPM unit for supporting a patient's leg through a range of motion, a drive means for moving the leg through the range of motion, and a NMS means for applying electrical stimulation to a muscle in the leg. The rehab apparatus further includes a controller for managing the operation of the CPM unit, drive means, and NMS means. In particular, the controller stops the drive means when the CPM unit is disposed in an extended position and initiates muscle stimulation for a time period in which the CPM unit remains stationary. However, the controller does not allow for varying the sequence or order of stimulation and passive motion which is beneficial for rehabilitating and re-educating muscle function and neurological function. Further, the rehab apparatus disclosed by Wright et al. does not provide prophylactic means for preventing DVT.
U.S. Pat. No. 5,399,147 to Kaiser discloses a CPM orthotic device comprising two carriage members receiving a limb, a hinge interconnecting the two carriage members, a drive means moving the two carriage members reciprocally about the hinge, and a brace. Kaiser further discloses two neuromuscular stimulators integrated with the CPM device, wherein a first stimulator provides muscle stimulation when the limb is fully extended and a second stimulator provides stimulation when the limb is fully contracted. Like the prior rehab apparatus, Kaiser's CPM device does not provide for different sequences of stimulation and passive motion. Moreover, with only two stimulators, NMS benefits only limited areas of the patent's limb.
Some efforts have been made to provide a rehab device combining passive motion with DVT prophylactic therapy. For example, U.S. patent application Publication No. 2011/0077560 to Jacofsky et al. discloses a CPM machine with an integrated mechanical DVT prophylaxis. The CPM machine comprises a base, at least one motor, a plurality of hinged frame rails for imparting passive motion, and a suspension structure for positioning a roller assembly, wherein the roller assembly provides mechanical DVT prophylactic therapy. Jocofsky et al. further discloses a monitoring system to detect blood flow in the limb and provide feedback control to the roller assembly. However, the DVT prophylaxis requires multiple mechanical components in order to achieve suitable prophylactic therapy. In particular, the roller assembly must include multiple rollers, a motor to operate the rollers, a mechanism to adjust the position of the roller assembly to the limb, and a spring to maintain proper pressure against the limb, all of which are necessary for imparting the desired rotational motion needed for prophylactic therapy. With all of its mechanical parts, the CPM machine remains cumbersome, difficult to maneuver and prone to mechanical failure. The CPM machine also lacks other modalities for promoting full range of motion, neurological function, and muscle function in the limb.
While the prior art CPM devices may provide benefits over conventional rehab and postoperative treatment devices, they still suffer from several disadvantages. One of such disadvantages is that the CPM devices do not provide a comprehensive, synergistic treatment of postoperative bodily parts for rehabilitation and re-education of neurological function, muscle function, and range of motion. The prior art CPM devices provide either a single modality or a limited number of modalities for therapeutic treatment. Furthermore, the CPM device and modalities are integrated independently such that the benefits of a coordinated therapy of the CPM and modalities are not achieved. As such, the treatment provided by prior art CPM devices fail to address multiple postoperative complications involved in joint surgeries and may subsequently prolong a patient's time for recovery.